FinFET Device and Method of Forming

ABSTRACT

A finFET device and a method of forming are provided. The device includes a transistor comprising a gate electrode and a first source/drain region next to the gate electrode, the gate electrode being disposed over a first substrate. The device also includes a first dielectric layer extending along the first source/drain region, and a second dielectric layer overlying the first dielectric layer. The device also includes a contact disposed in the first dielectric layer and in the second dielectric layer, the contact contacting the gate electrode and the first source/drain region. A first portion of the first dielectric layer extends between the contact and the gate electrode. The contact extends along a sidewall of the first portion of the first dielectric layer and a first surface of the first portion of the first dielectric layer, the first surface of the first portion being farthest from the first substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.15/363,273, filed on Nov. 29, 2016, which application is herebyincorporated herein by reference.

BACKGROUND

In the current process of miniaturizing semiconductor devices, low-kdielectric materials are desired as the inter-metal and/or inter-layerdielectric between conductive interconnects in order to reduce theresistive-capacitive (RC) delay in signal propagation due to capacitiveeffects. As such, the lower the dielectric layer constant of thedielectric, the lower the parasitic capacitance of adjacent conductivelines and the lower the RC delay of the integrated circuit (IC).

However, the materials that are currently being considered or used aslow-k dielectric materials are not ideal. In particular, in choosing amaterial based upon its k-value, and particularly based upon its low-kvalue, other characteristics, such as the hardness of the material orits strength, may not be ideal for use in a semiconductor manufacturingprocess. As such, improvements in processes that utilize low-kdielectric materials are desired.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a perspective view of a fin field effect transistor (finFET)device in accordance with some embodiments.

FIGS. 2-6 are cross sectional views of intermediate stages of forming afinFET device in accordance with some embodiments.

FIGS. 7A-7C, 8A-8C, 9A-9C, 10A-10C, 11A-11C, 12A-12C, 13A-13C, 14A-14C,15A-15C, 16A-16C, 17A-17C, 18A-18C, 19A-19C, 20A-20C, 21A-21C, 22A-22C,23A-23C, 24A-24C, 25A-25C, and 26A-26C, are cross sectional views ofintermediate stages of forming a finFET device in accordance with someembodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

FIGS. 2 through 26A-C are cross-sectional views of intermediate stagesin the manufacturing of FinFETs in accordance with exemplaryembodiments. FIGS. 2 through 6 illustrate reference cross-section A-Aillustrated in FIG. 1, except for multiple FinFETs. In FIGS. 7 through26A-C, figures ending with an “A” designation are illustrated along asimilar cross-section A-A; figures ending with a “B” designation areillustrated along a similar cross-section B/C-B/C and in a first regionon a substrate; and figures ending with a “C” designation areillustrated along a similar cross-section B/C-B/C and in a second regionon a substrate.

FIG. 2 illustrates a substrate 50. Substrate 50 may be a semiconductorsubstrate, such as a bulk semiconductor, a semiconductor-on-insulator(SOI) substrate, or the like, which may be doped (e.g., with a p-type oran n-type dopant) or undoped. The substrate 50 may be a wafer, such as asilicon wafer. Generally, an SOI substrate comprises a layer of asemiconductor material formed on an insulator layer. The insulator layermay be, for example, a buried oxide (BOX) layer, a silicon oxide layer,or the like. The insulator layer is provided on a substrate, typically asilicon or glass substrate. Other substrates, such as a multi-layered orgradient substrate may also be used. In some embodiments, thesemiconductor material of the substrate 50 may include silicon;germanium; a compound semiconductor including silicon carbide, galliumarsenic, gallium phosphide, indium phosphide, indium arsenide, and/orindium antimonide; an alloy semiconductor including SiGe, GaAsP, AlinAs,AlGaAs, GalnAs, GaInP, and/or GaInAsP; or combinations thereof.

The substrate 50 has a first region 50B and a second region 50C. Thefirst region 50B (which corresponds to subsequent figures ending in “B”)can be for forming n-type devices, such as NMOS transistors, such asn-type FinFETs. The second region 50C (which corresponds to subsequentfigures ending in “C”) can be for forming p-type devices, such as PMOStransistors, such as p-type FinFETs.

FIGS. 3 and 4 illustrate the formation of fins 52 and isolation regions54 between neighboring fins 52. In FIG. 3 fins 52 are formed in thesubstrate 50. In some embodiments, the fins 52 may be formed in thesubstrate 50 by etching trenches in the substrate 50. The etching may beany acceptable etch process, such as a reactive ion etch (RIE), neutralbeam etch (NBE), the like, or a combination thereof. The etch may beanisotropic.

In FIG. 4 an insulation material 54 is formed between neighboring fins52 to form the isolation regions 54. The insulation material 54 may bean oxide, such as silicon oxide, a nitride, the like, or a combinationthereof, and may be formed by a high density plasma chemical vapordeposition (HDP-CVD), a flowable CVD (FCVD) method (e.g., a CVD-basedmaterial deposition in a remote plasma system and post curing to make itconvert to another material, such as an oxide), the like, or acombination thereof. Other insulation materials formed by any acceptableprocess may be used. An anneal process may be performed once theinsulation material is formed. In the illustrated embodiment, theinsulation material 54 is silicon oxide formed by a FCVD process. Theinsulating material 54 may be referred to as isolation regions 54.Further in FIG. 5, a planarization process, such as a chemicalmechanical polish (CMP), may remove any excess insulation material 54and form top surfaces of the isolation regions 54 and top surfaces ofthe fins 52 that are coplanar.

FIG. 5 illustrates the recessing of the isolation regions 54 to formShallow Trench Isolation (STI) regions 54. The isolation regions 54 arerecessed such that fins 56 in the first region 50B and in the secondregion 50C protrude from between neighboring isolation regions 54.Further, the top surfaces of the isolation regions 54 may have a flatsurface as illustrated, a convex surface, a concave surface (such asdishing), or a combination thereof. The top surfaces of the isolationregions 54 may be formed flat, convex, and/or concave by an appropriateetch. The isolation regions 54 may be recessed using an acceptableetching process, such as one that is selective to the material of theisolation regions 54. For example, a chemical oxide removal using aCERTAS® etch or an Applied Materials SICONI tool or dilute hydrofluoric(dHF) acid may be used.

A person having ordinary skill in the art will readily understand thatthe process described with respect to FIGS. 2 through 5 is just oneexample of how fins 56 may be formed. In other embodiments, a dielectriclayer can be formed over a top surface of the substrate 50; trenches canbe etched through the dielectric layer; homoepitaxial structures can beepitaxially grown in the trenches; and the dielectric layer can berecessed such that the homoepitaxial structures protrude from thedielectric layer to form fins. In still other embodiments,heteroepitaxial structures can be used for the fins. For example, thesemiconductor strips 52 in FIG. 4 can be recessed, and a materialdifferent from the semiconductor strips 52 may be epitaxially grown intheir place. In an even further embodiment, a dielectric layer can beformed over a top surface of the substrate 50; trenches can be etchedthrough the dielectric layer; heteroepitaxial structures can beepitaxially grown in the trenches using a material different from thesubstrate 50; and the dielectric layer can be recessed such that theheteroepitaxial structures protrude from the dielectric layer to formfins 56. In some embodiments where homoepitaxial or heteroepitaxialstructures are epitaxially grown, the grown materials may be in situdoped during growth, which may obviate prior and subsequentimplantations although in situ and implantation doping may be usedtogether. Still further, it may be advantageous to epitaxially grow amaterial in an NMOS region different from the material in a PMOS region.In various embodiments, the fins 56 may comprise silicon germanium(Si_(x)Ge_(1-x), where x can be between approximately 0 and 100),silicon carbide, pure or substantially pure germanium, a III-V compoundsemiconductor, a II-VI compound semiconductor, or the like. For example,the available materials for forming III-V compound semiconductorinclude, but are not limited to, InAs, AlAs, GaAs, InP, GaN, InGaAs,InAlAs, GaSb, AlSb, AlP, GaP, and the like.

In FIG. 5, appropriate wells may be formed in the fins 56, fins 52,and/or substrate 50. For example, a P well may be formed in the firstregion 50B, and an N well may be formed in the second region 50C.

The different implant steps for the different regions 50B and 50C may beachieved using a photoresist or other masks (not shown). For example, aphotoresist is formed over the fins 56 and the isolation regions 54 inthe first region 50B. The photoresist is patterned to expose the secondregion 50C of the substrate 50, such as a PMOS region. The photoresistcan be formed by using a spin-on technique and can be patterned usingacceptable photolithography techniques. Once the photoresist ispatterned, an n-type impurity implant is performed in the second region50C, and the photoresist may act as a mask to substantially preventn-type impurities from being implanted into the first region 50B, suchas an NMOS region. The n-type impurities may be phosphorus, arsenic, orthe like implanted in the first region to a concentration of equal to orless than 10¹⁸ cm⁻³, such as in a range from about 10¹⁷ cm⁻³ to about10¹⁸ cm⁻³. After the implant, the photoresist is removed, such as by anacceptable ashing process.

Following the implanting of the second region 50C, a photoresist isformed over the fins 56 and the isolation regions 54 in the secondregion 50C. The photoresist is patterned to expose the first region 50Bof the substrate 50, such as the NMOS region. The photoresist can beformed by using a spin-on technique and can be patterned usingacceptable photolithography techniques. Once the photoresist ispatterned, a p-type impurity implant may be performed in the firstregion 50B, and the photoresist may act as a mask to substantiallyprevent p-type impurities from being implanted into the second region,such as the PMOS region. The p-type impurities may be boron, BF₂, or thelike implanted in the first region to a concentration of equal to orless than 10¹⁸ cm⁻³, such as in a range from about 10¹⁷ cm⁻³ to about10¹⁸ cm⁻³. After the implant, the photoresist may be removed, such as byan acceptable ashing process.

After the implants of the first region 50B and the second region 50C, ananneal may be performed to activate the p-type and n-type impuritiesthat were implanted. The implantations may form a p-well in the firstregion 50B, e.g., the NMOS region, and an n-well in the second region50C, e.g., the PMOS region. In some embodiments, the grown materials ofepitaxial fins may be in situ doped during growth, which may obviate theimplantations, although in situ and implantation doping may be usedtogether.

In FIG. 6, a dummy dielectric layer 58 is formed on the fins 56. Thedummy dielectric layer 58 may be, for example, silicon oxide, siliconnitride, a combination thereof, or the like, and may be deposited orthermally grown according to acceptable techniques. A dummy gate layer60 is formed over the dummy dielectric layer 58, and a mask layer 62 isformed over the dummy gate layer 60. The dummy gate layer 60 may bedeposited over the dummy dielectric layer 58 and then planarized, suchas by a CMP. The mask layer 62 may be deposited over the dummy gatelayer 60. The dummy gate layer 60 may be made of, for example,polysilicon, although other materials that have a high etchingselectivity from the etching of isolation regions 54 may also be used.The mask layer 62 may include, for example, silicon nitride or the like.In this example, a single dummy gate layer 60 and a single mask layer 62are formed across the first region 50B and the second region 50C. Inother embodiments, separate dummy gate layers may be formed in the firstregion 50B and the second region 50C, and separate mask layers may beformed in the first region 50B and the second region 50C.

In FIGS. 7A, 7B, and 7C, the mask layer 62 may be patterned usingacceptable photolithography and etching techniques to form masks 72 inthe first region 50B and masks 78 in the second region 50C. The patternof the masks 72 and 78 then may be transferred to the dummy gate layer60 and dummy dielectric layer 58 by an acceptable etching technique toform dummy gates 70 in the first region 50B and dummy gates 76 in thesecond region 50C. The dummy gates 70 and 76 cover respective channelregions of the fins 56. The dummy gates 70 and 76 may also have alengthwise direction substantially perpendicular to the lengthwisedirection of respective epitaxial fins.

In FIGS. 8A, 8B, and 8C, gate seal spacers 80 can be formed on exposedsurfaces of respective dummy gates 70 and 76 and/or fins 56. A thermaloxidation or a deposition followed by an anisotropic etch may form thegate seal spacers 80.

After the formation of the gate seal spacers 80, implants for lightlydoped source/drain (LDD) regions may be performed. Similar to theimplants discussed above in FIG. 5, a mask, such as a photoresist, maybe formed over the first region 50B, e.g., NMOS region, while exposingthe second region 50C, e.g., PMOS region, and p-type impurities may beimplanted into the exposed fins 56 in the second region 50C. The maskmay then be removed. Subsequently, a mask, such as a photoresist, may beformed over the second region 50C while exposing the first region 50B,and n-type impurities may be implanted into the exposed fins 56 in thefirst region 50B. The mask may then be removed. The n-type impuritiesmay be the any of the n-type impurities previously discussed, and thep-type impurities may be the any of the p-type impurities previouslydiscussed. The lightly doped source/drain regions may have aconcentration of impurities of from about 10¹⁵ cm⁻³ to about 10¹⁶ cm⁻³.An anneal may be used to activate the implanted impurities.

Further in FIGS. 8A, 8B, and 8C, epitaxial source/drain regions 82 and84 are formed in the fins 56. In the first region 50B, epitaxialsource/drain regions 82 are formed in the fins 56 such that each dummygate 70 is disposed between respective neighboring pairs of theepitaxial source/drain regions 82. In some embodiments that epitaxialsource/drain regions 82 may extend into the fins 52. In the secondregion 50C, epitaxial source/drain regions 84 are formed in the fins 56such that each dummy gate 76 is disposed between respective neighboringpairs of the epitaxial source/drain regions 84. In some embodiments thatepitaxial source/drain regions 84 may extend into the fins 52.

Epitaxial source/drain regions 82 in the first region 50B, e.g., theNMOS region, may be formed by masking the second region 50C, e.g., thePMOS region, and conformally depositing a dummy spacer layer in thefirst region 50B followed by an anisotropic etch to form dummy gatespacers (not shown) along sidewalls of the dummy gates 70 and/or gateseal spacers 80 in the first region 50B. Then, source/drain regions ofthe epitaxial fins in the first region 50B are etched to form recesses.The epitaxial source/drain regions 82 in the first region 50B areepitaxially grown in the recesses. The epitaxial source/drain regions 82may include any acceptable material, such as appropriate for n-typeFinFETs. For example, if the fin 56 is silicon, the epitaxialsource/drain regions 82 may include silicon, SiC, SiCP, SiP, or thelike. The epitaxial source/drain regions 82 may have surfaces raisedfrom respective surfaces of the fins 56 and may have facets.Subsequently, the dummy gate spacers in the first region 50B areremoved, for example, by an etch, as is the mask on the second region50C.

Epitaxial source/drain regions 84 in the second region 50C, e.g., thePMOS region, may be formed by masking the first region 50B, e.g., theNMOS region, and conformally depositing a dummy spacer layer in thesecond region 50C followed by an anisotropic etch to form dummy gatespacers (not shown) along sidewalls of the dummy gates 76 and/or gateseal spacers 80 in the second region 50C. Then, source/drain regions ofthe epitaxial fins in the second region 50C are etched to form recesses.The epitaxial source/drain regions 84 in the second region 50C areepitaxially grown in the recesses. The epitaxial source/drain regions 84may include any acceptable material, such as appropriate for p-typeFinFETs. For example, if the fin 56 is silicon, the epitaxialsource/drain regions 84 may comprise SiGe, SiGeB, Ge, GeSn, or the like.The epitaxial source/drain regions 84 may have surfaces raised fromrespective surfaces of the fins 56 and may have facets. Subsequently,the dummy gate spacers in the second region 50C are removed, forexample, by an etch, as is the mask on the first region 50B.

In FIGS. 9A, 9B, and 9C, gate spacers 86 are formed on the gate sealspacers 80 along sidewalls of the dummy gates 70 and 76. The gatespacers 86 may be formed by conformally depositing a material andsubsequently anisotropically etching the material. The material of thegate spacers 86 may be silicon nitride, SiCN, a combination thereof, orthe like.

The epitaxial source/drain regions 82 and 84 and/or epitaxial fins maybe implanted with dopants to form source/drain regions, similar to theprocess previously discussed for forming lightly doped source/drainregions, followed by an anneal. The source/drain regions may have animpurity concentration of in a range from about 10¹⁹ cm⁻³ to about 10²¹cm⁻³. The n-type impurities for source/drain regions in the first region50B, e.g., the NMOS region, may be any of the n-type impuritiespreviously discussed, and the p-type impurities for source/drain regionsin the second region 50C, e.g., the PMOS region, may be any of thep-type impurities previously discussed. In other embodiments, theepitaxial source/drain regions 82 and 84 may be in situ doped duringgrowth.

In FIGS. 10A, 10B, and 10C, an ILD 88 is deposited over the structureillustrated in FIGS. 9A, 9B and 9C. In an embodiment, the ILD 88 is afilm formed by a flowable CVD method. In some embodiments, the ILD 88 isformed of a dielectric material such as Phospho-Silicate Glass (PSG),Boro-Silicate Glass (BSG), Boron-Doped Phospho-Silicate Glass (BPSG),undoped Silicate Glass (USG), or the like, and may be deposited by anysuitable method, such as CVD, or PECVD.

In FIGS. 11A, 11B, and 11C, a planarization process, such as a CMP, maybe performed to level the top surface of ILD 88 with the top surfaces ofthe dummy gates 70 and 76. The CMP may also remove the masks 72 and 78on the dummy gates 70 and 76. Accordingly, top surfaces of the dummygates 70 and 76 are exposed through the ILD 88.

In FIGS. 12A, 12B, and 12C, the dummy gates 70 and 76, gate seal spacers80, and portions of the dummy dielectric layer 58 directly underlyingthe dummy gates 70 and 76 are removed in an etching step(s), so thatrecesses 90 are formed. Each recess 90 exposes a channel region of arespective fin 56. Each channel region is disposed between neighboringpairs of epitaxial source/drain regions 82 and 84. During the removal,the dummy dielectric layer 58 may be used as an etch stop layer when thedummy gates 70 and 76 are etched. The dummy dielectric layer 58 and gateseal spacers 80 may then be removed after the removal of the dummy gates70 and 76.

In FIGS. 13A, 13B, and 13C, gate dielectric layers 92 and 96 are formedfor replacement gates. Gate dielectric layers 92 and 96 are depositedconformally in recesses 90, such as on the top surfaces and thesidewalls of the fins 56 and on sidewalls of the gate spacers 86, and ona top surface of the ILD 88. In accordance with some embodiments, gatedielectric layers 92 and 96 comprise silicon oxide, silicon nitride, ormultilayers thereof. In other embodiments, gate dielectric layers 92 and96 include a high-k dielectric material, and in these embodiments, gatedielectric layers 92 and 96 may have a k value greater than about 7.0,and may include a metal oxide or a silicate of Hf, Al, Zr, La, Mg, Ba,Ti, Pb, and combinations thereof. The formation methods of gatedielectric layers 92 and 96 may include Molecular-Beam Deposition (MBD),Atomic Layer Deposition (ALD), PECVD, and the like.

Next, gate electrodes 94 and 98 are deposited over gate dielectriclayers 92 and 96, respectively, and fill the remaining portions of therecesses 90. Gate electrodes 94 and 98 may be made of a metal-containingmaterial such as TiN, TaN, TaC, Co, Ru, Al, combinations thereof, ormulti-layers thereof. After the filling of gate electrodes 94 and 98,excess metal-containing material is disposed over the recesses 90 andextends along sections of gate dielectric layers 92 and 96 that extendalong a top surface of ILD 88. The resulting structure is depicted inFIGS. 13A, 13B, and 13C.

The formation of the gate dielectric layers 92 and 96 may occursimultaneously such that the gate dielectric layers 92 and 96 are madeof the same materials, and the formation of the gate electrodes 94 and98 may occur simultaneously such that the gate electrodes 94 and 98 aremade of the same materials. However, in other embodiments, the gatedielectric layers 92 and 96 may be formed by distinct processes, suchthat the gate dielectric layers 92 and 96 may be made of differentmaterials, and the gate electrodes 94 and 98 may be formed by distinctprocesses, such that the gate electrodes 94 and 98 may be made ofdifferent materials. Various masking steps may be used to mask andexpose appropriate regions when using distinct processes.

Next, a planarization process, such as a CMP, may be performed to removethe excess portions of gate dielectric layers 92 and 96 and the excessmaterial of gate electrodes 94 and 98. For example a planarizationprocess may be performed to remove any excess portions that are over thetop surface of ILD 88. The resulting structure is depicted in FIGS.14A-C. The resulting remaining portions of material of gate electrodes94 and 98 and gate dielectric layers 92 and 96 thus form replacementgates of the resulting FinFETs.

In some embodiments, the planarization process may continue until a topportion of gate spacers 86 are removed and an overall height of ILD 88and gate electrodes 94 and 98 are reduced. For example, before theplanarization process, gate spacers may have a height H1 of about 400 Åto about 600 Å, such as about 500 Å. After the planarization process,gate spacers 86 may have a height H1 of about 150 Å to about 200 Å, suchas about 180 Å. In some embodiments, the duration of the planarizationprocess may be determined according to a thickness of ILD 88.

In FIGS. 15A, 15B, and 15C, an ILD 100 is deposited over ILD 88. In someembodiments, the ILD 100 is a film that is formed by a flowable CVDmethod. In some embodiments, the ILD 100 is formed of a dielectricmaterial such as PSG, BSG, BPSG, USG, or the like, and may be depositedby any suitable method, such as CVD and PECVD. In some embodiments, ILD100 may have a thickness T1 of about 650 Å to about 750 Å, such as about700 Å.

FIGS. 16A-C through 26A-C depict intermediate stages in the formation ofan electrically conductive connector that connects an epitaxialsource/drain region 82/84 to a gate electrode 94/98, and that mayconnect the connected epitaxial source/drain region 82/84 and gateelectrode 94/98 to other components in an electrical circuit. Forexample, in some applications it may be desirable to utilize in anelectrical circuit a transistor in which a source terminal is connectedto a gate terminal, or in which a drain terminal is connected to a gateterminal.

As depicted in FIGS. 16A-C to 26A-C, an electrical connector may beformed by first patterning ILD 100 to expose the gate electrode 94/98and then patterning ILD 88 through the patterned ILD 100 to expose theepitaxial source/drain region 82/84. By first patterning ILD 100 toexpose the gate electrode 94/98 and then patterning ILD 88 through thepatterned ILD 100 to expose the epitaxial source/drain region 82/84, itmay possible to avoid or reduce the use of a plasma etching process(es).If a plasma etching process is used, then the plasma etching process mayleave behind residue in the openings created by the plasma etchingprocess. A cleaning process (e.g., an oxygen treatment) may need to beperformed to remove the residue created by the plasma etching. However,the oxygen treatment may cause oxidation of ILD 88 and/or ILD 100 in theopening, which may negatively impact the RC constant of the FinFET. Byavoiding a plasma etching process, the residue and the subsequentoxidation of the ILD layers from the oxygen treatment may be avoided orminimized. Further, by first patterning the ILD 100 to expose the gateelectrode 94/98 and then patterning ILD 88 through the patterned ILD 100to expose the epitaxial source/drain region 82/84, it may be possible toavoid a process of depositing a sacrificial film over the gate electrode94/98 to protect the gate electrode 94/98 during a plasma etchingprocess. By avoiding the need to deposit the sacrificial film,manufacturing may be streamlined and costs may be minimized.

Referring to FIGS. 16A-C, a first step of a first tri-layer photo resistprocess is depicted. In the first step of the first tri-layer photoresist process, three layers (150, 152, and 154) are deposited over ILD100 using a suitable process, such as, sputtering, spin-on coating, orthe like. In subsequent steps, the three layers (150, 152, and 154) willbe patterned to form an opening that exposes ILD 100 over gateelectrodes 94/98 and a portion of ILD 100 that overlies an epitaxialsource/drain region 82/84 to which the gate electrodes 94/98 will beelectrically connected. (See FIGS. 17A, 17B, 17C). The three layersinclude a bottom anti-reflective coating (BARC) layer 150, anintermediate hard mask layer 152, and a top photoresist layer 154. Inother embodiments, other types of patterning masks may be used, whichmay include fewer or a greater number of layers than the tri-layer photoresist process depicted herein.

Referring to FIGS. 17A, 17B, and 17C, the top photoresist layer 154 maybe patterned to expose one or more portions of ILD 100 that overliesgate electrodes 94/98. The patterning may also expose a section of ILD100 that overlies an epitaxial source/drain region 82/84 to which thegate electrode 94/98 will be connected. Top photoresist layer 154 may bepatterned using any suitable photolithography technique. For example, aphotomask (not shown) may be disposed over the top photoresist layer154, which may then be exposed to a radiation beam including anultraviolet (UV) or an excimer laser such as a 248 nm beam from aKrypton Fluoride (KrF) excimer laser, a 193 nm beam from an ArgonFluoride (ArF) excimer laser, or a 157 nm beam from a F₂ excimer laser.Exposure of the top photoresist layer 154 may be performed using animmersion lithography system to increase resolution and decrease theminimum achievable pitch. A bake or cure operation may be performed toharden the top photoresist layer 154, and a developer may be used toremove either the exposed or unexposed portions of the top photoresistlayer 154 depending on whether a positive or negative resist is used.After the patterning of the top photoresist layer 154, a trimmingprocess may be performed to reduce the width of the top photoresistlayer 154. In an embodiment, the trimming process is an anisotropicplasma etch process with process gases including O₂, CO₂, N₂/H₂, H₂, thelike, a combination thereof, or any other gases suitable for trimmingphotoresist. After the trimming process, the intermediate hard masklayer 152 and the BARC layer 150 may be patterned (e.g., using anetching process), leaving the pattern illustrated in FIGS. 17A, 17B, and17C. As part of the patterning process, portions of the top photoresistlayer 154 may be consumed. For example, after patterning theintermediate hard mask layer 152 and the BARC layer 150, a thickness ofthe top photoresist layer 154 may be reduced.

Next, referring to FIGS. 18A, 18B, and 18C, the ILD 100 is patternedusing remaining portions of the three layers (layers 150, 152, and 154)as a mask to form openings 156. Openings 156 expose at least a portionof the top surfaces of gate electrodes 94/98. In some embodiments, onlya portion of a top surface of a gate electrode 94/98, measured from adirection that extends from a first gate spacer 86 to a second gatespacer 86, may be exposed by openings 156. For example, in someembodiments a portion of a top surface of a gate electrode 94/98 that isclosest to an epitaxial source/drain region 82/84 to which the gateelectrode 94/98 will be electrically connected will be exposed by anopening 156. In some embodiments, the entire top surface of a gateelectrode 94/98 between two adjacent gate spacers 86 may be exposed byan opening 156. As shown in FIGS. 18A, 18B and 18C, openings 156 mayalso expose an area of ILD 88 that overlies at least a portion of acorresponding epitaxial source/drain region 82/84 to which the gateelectrodes 94/98 will be electrically connected.

The patterning of the ILD 100 to form the openings 156 may be performedusing any kind of suitable etching technique. In some embodiments, a wetetching process that has a high selectivity between oxides and tungstenmay be used. The etching process may continue until an end point isdetected. For example, in some embodiments the detection of the gateelectrode 94/98 may signal an endpoint of the etching process. In someembodiments it may be desirable to avoid the use of a plasma etchingprocess to avoid the creation of residue in openings 156.

After the etching process, openings 156 may have tapered sidewalls asdepicted in FIGS. 18A, 18B, and 18C. In some embodiments, sidewalls ofopenings 156 may form an angle with a bottom surface of openings 156 ofabout 93 degrees to about 98 degrees, such as about 95 degrees.

Next, the three layers 150, 152 and 154 of the first tri-layerphotoresist process are removed, for example in an ashing process. Anoptional wet clean may also be applied to remove the three layers 150,152, and 154. The resulting structure is depicted in FIGS. 19A, 19B, and19C.

Referring to FIGS. 20A, 20B and 20C, a second tri-layer photoresistprocess is begun by depositing another three layers (158, 160, and 162)over ILD 100 and over ILD 88/gate electrode 94/98/gate spacer 86 inopenings 156. In subsequent steps, the three layers (158, 160, and 162)will be patterned to form an opening that exposes ILD 88 over theportion of the epitaxial source/drain region 82/84 to which the gateelectrode 94/98 will be electrically connected. (See FIGS. 21A, 21B,21C). As discussed in detail above, the three layers include a bottomanti-reflective coating (BARC) layer 158, an intermediate hard masklayer 160, and a top photoresist layer 162. The bottom BARC layersubstantially fills openings 156 and creates a substantially planarsurface upon which the intermediate hard mask layer 160 and the topphotoresist layer 162 may be formed. The three layers 158, 160, and 162may be deposited using a non-conformal deposition process, such as,sputtering, spin-on coating, or the like. In other embodiments, othertypes of patterning masks may be used, which may include fewer or agreater number of layers than the tri-layer photo resist processdepicted herein.

Referring to FIGS. 21A, 21B, and 21C, the top photoresist layer 162 maybe patterned to expose one or more portions of ILD 88 that overlies theportion of epitaxial source/drain region 82/84 to which the gateelectrode 94/98 will be electrically connected. Top photoresist layer162 may be patterned using any suitable photolithography technique, suchas the techniques described above in connection with the first tri-layerphotolithography process. After the patterning of the top photoresistlayer 162, the intermediate hardmask layer 160 and the BARC layer 158may be patterned, leaving the pattern illustrated in FIGS. 21A, 21B, and21C.

In some embodiments, because of the first tri-layer photolithographyprocess to create openings 156 (see FIGS. 19A-19C), the three layers158, 160 and 162 of the second tri-layer photoresist process may bepatterned in a manner than directly exposes ILD 88 through an opening156 (shown in FIGS. 19A, 19B, 19C) that was previously created in ILD100. For example, in some embodiments, after the patterning of the threelayers 158, 160 and 162 of the second tri-layer photoresist process,sidewalls of an opening in ILD 100 may extend on at least two sides ofopenings in the three layers 158, 160 and 162. In some embodiments,layers 158, 160 and 162 may be patterned to expose only ILD 88 and notany portions of ILD 100. In some embodiments, the three layers 158, 160and 162 of the second tri-layer photoresist process may be patterned ina manner that exposes portions of ILD 100 in addition to ILD 88.

Next, referring to FIGS. 22A, 22B, and 22C, ILD 88 is patterned usinglayers 158, 160, and 162 as a mask to form openings 164. Openings 164extend openings 156 in ILD 100 (See FIGS. 19A, 19B, and 19C) thatexposes a gate electrode 94/98 to also expose a portion of the epitaxialsource/drain region 82/84 to which the gate electrode 94/98 will beelectrically connected (See FIGS. 24A-24C). In some embodiments,openings 164 expose only a portion of a top surface of the epitaxialsource/drain region 82/84. In some embodiments, a whole top surface ofan epitaxial source/drain region 82/84 may be exposed by an opening 164.As shown in FIGS. 22A, 22B and 22C, in some embodiments ILD 88 extendsalong sidewalls of openings 164. In some embodiments, ILD 88 may extendbetween an opening 164 and a gate spacer 86. In some embodiments,openings 164 may have tapered sidewalls. In some embodiments, sidewallsof openings 164 may form an angle with a bottom surface of openings 164of about 90 degrees to about 95 degrees, such as about 92 degrees.

ILD 88 may be patterned using layers 158, 160, and 162 as a mask to formopenings 164 using any suitable etching process. In some embodiments,atomic layer etching may be used. In some embodiments, a duration of theetching process for performing the etch may be calculated according toprocess parameters. In some embodiments, over etching may be used wherethe etching process continues past the calculated duration, such as anover etching of 33%. In some embodiments it may be desirable to avoidthe use of a plasma etching process to avoid the creation of residue inopenings 164.

Referring to FIGS. 23A, 23B and 23C, layers 158, 160 and 162 areremoved, for example using an ashing process. The resulting structure isdepicted in FIGS. 23A, 23B and 23C. ILD 88 and ILD 100 have beenpatterned to create an opening 166 that exposes at least a portion of agate electrode 94/98 and at least a portion of an epitaxial source/drainregion 82/84. Opening 166 may have a first sidewall that extends alongboth ILD 100 and ILD 88. Opening 166 may have a second sidewall thatextends along only ILD 88 and a third sidewall that extends along onlyILD 100. A bottom surface of opening 166 may extend along gate electrode98/94, ILD 88 and gate dielectric layer 92/96. A section of ILD 88 mayextend between the second sidewall of opening 166 and a gate spacer 86.After the creation of opening 166, gate electrodes 94/98 may have aheight H2 of 150A to 200A, such as about 180 Å. After the secondpatterning process to create opening 166, an angle between a top surfaceof a gate electrode 94/98 and a sidewall of the gate electrode 94/98 inopening 166 may be substantially perpendicular.

FIGS. 24A-C through 26A-C depict the formation of an electricalconnector 174 (See FIGS. 26A-C) that is formed in an opening 166. First,FIGS. 24A-C illustrate the formation of a barrier layer 170 in openings166. Barrier layer 170 may cover sidewalls and a bottom surface ofopenings 166. Barrier layer 170 may comprise, for example, titaniumnitride, titanium oxide, tantalum nitride, tantalum oxide or the like.Barrier layer 170 may be deposited using any suitable depositionprocess, such as CVD, PVD, a conformal deposition process, or the like.

FIGS. 25A-C illustrate the filling of openings 166 with a metallicmaterial 172 such as copper, a copper alloy, tungsten, aluminum, oranother suitable conductor. The deposition of the metallic material 172may overflow opening 166 and extend along a top surface of ILD 100.Subsequently, as illustrated by FIGS. 26A-26C, a planarization (e.g.,CMP or etch back) maybe used to remove overflow portions. The resultingstructure is depicted in FIGS. 26A-26C.

As shown in FIGS. 26A-26C, electrical connector 174 may have a profilethat conforms to the profile of opening 166 (shown in FIGS. 23A-23C).Electrical connector 174 may physically contact gate electrode 94/98 andan epitaxial source/drain region 82/84, thereby forming an electricalconnection between gate electrode 94/98 and epitaxial source/drainregion 82/84.

Although not explicitly shown, a person having ordinary skill in the artwill readily understand that further processing steps may be performedon the structure in FIGS. 26A, 26B, and 26C. In subsequent processing,additional ILD or Inter-Metal Dielectrics (IMD) layers may be depositedover ILD 100. Interconnects may be formed in overlying ILD or IMD layersto contact electrical connector 174, which may allow electricalconnector 174 to electrically connect to other components in a samepackage or in a different package.

As described above, an electrical connector is formed that electricallyconnects an epitaxial source/drain region to a gate electrode. In someembodiments, a second dielectric layer is patterned to expose the gateelectrode, and then a first dielectric layer is patterned through anopening created in the second dielectric layer to expose the epitaxialsource/drain region. By patterning the second dielectric layer to exposethe gate electrode, and then patterning the first dielectric layer toexpose the epitaxial source/drain region, it may possible to avoid theuse of a plasma etching process. If a plasma etching process is used,then the plasma etching process may leave behind residue in the openingscreated by the plasma etching process. An oxygen treatment may need tobe performed to remove the residue created by the plasma etching.However, the oxygen treatment may cause oxidation of the firstdielectric layer and/or the second dielectric layer in the opening,which may negatively impact the RC constant of the finFET. By avoiding aplasma etching process, the residue and the subsequent oxidation of theILD layers from the oxygen treatment may be avoided or minimized.Further, by first patterning the second dielectric layer to expose thegate electrode and then patterning the first dielectric layer to exposethe epitaxial source/drain region, it may be possible to avoid a processof depositing a sacrificial film over the gate electrode to protect thegate electrode during the plasma etching process. By avoiding the needto deposit the sacrificial film, manufacturing may be streamlined andcosts may be minimized.

According to some embodiments, a method is provided. The method includesforming a first dielectric layer over a transistor. The method alsoincludes forming a second dielectric layer over the first dielectriclayer. The method also includes forming a first opening in the seconddielectric layer to expose at least a portion of a gate electrode of thetransistor. The method also includes forming a second opening in thefirst dielectric layer to expose at least a portion of a source/drainregion of the transistor. The second opening is connected to the firstopening, and the first opening is formed before the second opening. Themethod also includes forming an electrical connector in the firstopening and the second opening.

According to some embodiments, a method is provided. The method includesforming fin field effect transistor (finFET). The finFET includes a gatestructure and a plurality of source/drain regions. The method alsoincludes forming a first dielectric layer over the finFET. The methodalso includes planarizing a top surface of the first dielectric layerand a top surface of the gate structure. The method also includesforming a second dielectric layer over the first dielectric layer andthe gate structure. The method also includes etching the seconddielectric layer to form a first opening that exposes at least a portionof a gate electrode of the gate structure and a section of the firstdielectric layer that overlies one of the plurality of source/drainregions. The method also includes etching the first dielectric layerthrough the first opening to expose at least a portion of the one of theplurality of source/drain regions. The method also includes forming anelectrical connector in the first dielectric layer and the seconddielectric layer, the electrical connector contacting the gate electrodeand the portion of the one of the plurality of source/drain regions.

According to some embodiments a device is provided. The device includesa transistor including a gate structure and a plurality of source/drainregions. The device also includes a first dielectric layer extendingalong the gate structure and the plurality of source/drain regions. Thedevice also includes a second dielectric layer overlying the firstdielectric layer. The device also includes an electrical connectordisposed in the first dielectric layer and in the second dielectriclayer, the electrical connector contacting the gate structure and one ofthe plurality of source/drain regions. The first dielectric layerextends between an interface of the electrical connector and the one ofthe plurality of source/drain regions and an interface of the electricalconnector and the gate structure, and an angle formed by the interfaceof the electrical connector and the gate structure and a sidewall of agate electrode of the gate structure is substantially perpendicular.

A device is provided in accordance with some embodiments. The deviceincludes a transistor comprising a gate electrode and a firstsource/drain region next to the gate electrode, the gate electrode beingdisposed over a first substrate. The device also includes a firstdielectric layer extending along the first source/drain region. Thedevice also includes a second dielectric layer overlying the firstdielectric layer. The device also includes a contact disposed in thefirst dielectric layer and in the second dielectric layer, the contactcontacting the gate electrode and the first source/drain region. A firstportion of the first dielectric layer extends between the contact andthe gate electrode. The contact extends along a sidewall of the firstportion of the first dielectric layer and a first surface of the firstportion of the first dielectric layer, the first surface of the firstportion being farthest from the first substrate.

A device is provided in accordance with some embodiments. The deviceincludes a transistor comprising a gate structure and a plurality ofsource/drain regions. The device also includes a first dielectric layerextending along the gate structure and the plurality of source/drainregions. The device also includes a second dielectric layer overlyingthe first dielectric layer. The device also includes an electricalconnector disposed in the first dielectric layer and in the seconddielectric layer, the electrical connector contacting the gate structureand a first source/drain region of the plurality of source/drainregions. The first dielectric layer extends between a first interfaceand a second interface, the first interface being an interface of theelectrical connector and the first source/drain region, and the secondinterface being an interface of the electrical connector and the gatestructure. An angle formed by the second interface and a sidewall of agate electrode of the gate structure is substantially perpendicular.

A device is provided in accordance with some embodiments. The deviceincludes a transistor comprising a gate structure and a plurality ofsource/drain regions. The device also includes a plurality of dielectriclayers overlying the transistor. The device also includes an electricalconnector extending through the plurality of dielectric layers, theelectrical connector contacting a gate electrode of the gate structureand a first source/drain region of the plurality of source/drainregions. A first portion of the plurality of dielectric layers extendsbetween the electrical connector and the gate structure, and between thefirst source/drain region and the gate structure. The first portion ofthe plurality of dielectric layers contacts the electrical connector ona first surface of the first portion and a second surface of the firstportion, the first surface of the first portion being non-planar withthe second surface of the first portion. A shape of the first portion,in a cross-sectional view, is defined by the gate structure, the firstsource/drain region, and the electrical connector.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A device, comprising: a transistor comprising agate electrode and a first source/drain region next to the gateelectrode, the gate electrode being disposed over a first substrate; afirst dielectric layer extending along the first source/drain region; asecond dielectric layer overlying the first dielectric layer; a contactdisposed in the first dielectric layer and in the second dielectriclayer, the contact contacting the gate electrode and the firstsource/drain region, wherein a first portion of the first dielectriclayer extends between the contact and the gate electrode, and whereinthe contact extends along a sidewall of the first portion of the firstdielectric layer and a first surface of the first portion of the firstdielectric layer, the first surface of the first portion being farthestfrom the first substrate.
 2. The device according to claim 1, whereinthe sidewall is tapered.
 3. The device according to claim 1, wherein thesecond dielectric layer contacts a first surface of the gate electrode,and wherein the first surface of the gate electrode is substantiallyparallel to a major surface of the first substrate.
 4. The deviceaccording to claim 1, wherein a surface of the contact that is farthestfrom the first substrate is substantially planar with a major surface ofthe second dielectric layer that is farthest from the first substrate.5. A device, comprising: a transistor comprising a gate structure and aplurality of source/drain regions; a first dielectric layer extendingalong the gate structure and the plurality of source/drain regions; asecond dielectric layer overlying the first dielectric layer; anelectrical connector disposed in the first dielectric layer and in thesecond dielectric layer, the electrical connector contacting the gatestructure and a first source/drain region of the plurality ofsource/drain regions, wherein the first dielectric layer extends betweena first interface and a second interface, the first interface being aninterface of the electrical connector and the first source/drain region,and the second interface being an interface of the electrical connectorand the gate structure, and wherein an angle formed by the secondinterface and a sidewall of a gate electrode of the gate structure issubstantially perpendicular.
 6. The device according to claim 5, whereina top surface of the gate structure is substantially planar with a topsurface of the first dielectric layer.
 7. The device according to claim5, wherein the electrical connector comprises one or more taperedsidewalls.
 8. The device according to claim 5, wherein a bottom surfaceof the electrical connector extends along a gate electrode, a gatedielectric layer, a gate spacer, and the first dielectric layer.
 9. Thedevice according to claim 5, wherein a continuous sidewall of theelectrical connector extends along the first dielectric layer and thesecond dielectric layer.
 10. The device according to claim 5, whereinthe gate structure comprises a gate electrode, the electrical connectorcontacts and extends along a first portion of a first surface of thegate electrode, and the second dielectric layer contacts and extendsalong a second portion of the first surface of the gate electrode. 11.The device according to claim 5, wherein the electrical connectorcomprises a barrier layer and a conductive material overlying thebarrier layer.
 12. The device according to claim 5, wherein theelectrical connector contacts and extends along a first portion of afirst surface of the first source/drain region, and the first dielectriclayer contacts and extends along a second portion of the first surfaceof the first source/drain region.
 13. The device according to claim 12,wherein a sidewall of the electrical connector extends in asubstantially straight line between the first surface of the firstsource/drain region and a surface of the second dielectric layer that isfurthest from the first source/drain region.
 14. The device according toclaim 12, wherein the second portion of the first surface of the firstsource/drain region is further from the gate structure than the firstinterface.
 15. The device according to claim 12, wherein the secondportion of the first surface of the first source/drain region is closerto the gate structure than the first interface.
 16. The device accordingto claim 12, wherein a thickness of the electrical connector in thesecond dielectric layer is greater than a thickness of the electricalconnector in the first dielectric layer.
 17. A device, comprising: atransistor comprising a gate structure and a plurality of source/drainregions; a plurality of dielectric layers overlying the transistor; anelectrical connector extending through the plurality of dielectriclayers, the electrical connector contacting a gate electrode of the gatestructure and a first source/drain region of the plurality ofsource/drain regions, wherein a first portion of the plurality ofdielectric layers extends between the electrical connector and the gatestructure, and between the first source/drain region and the gatestructure, wherein the first portion of the plurality of dielectriclayers contacts the electrical connector on a first surface of the firstportion and a second surface of the first portion, the first surface ofthe first portion being non-planar with the second surface of the firstportion, and wherein a shape of the first portion, in a cross-sectionalview, is defined by the gate structure, the first source/drain region,and the electrical connector.
 18. The device according to claim 17,wherein a first surface of the first portion of the plurality ofdielectric layers is planar with a surface of the gate electrode. 19.The device according to claim 17, wherein the electrical connectorcontacts a first surface of the first source/drain region, the firstportion of the plurality of dielectric layers contacts the first surfaceof the first source/drain region, and a second portion of the pluralityof dielectric layers contacts the first surface of the firstsource/drain region, wherein the first portion of the plurality ofdielectric layers is separated from the second portion of the pluralityof dielectric layers by a portion of the electrical connector.
 20. Thedevice according to claim 17, wherein a surface of the electricalconnector that contacts the first source/drain region has a dimensionthat is greater than a surface of the electrical connector that isfarthest from the first source/drain region.